Scientists at The Institute of Cancer Research, London, used the tool to analyse immune cell ‘hotspots’ in tumour samples from 1,178 women with oestrogen receptor positive (ER+) breast cancer, finding that those with a high number of hotspots were much more likely to see their breast cancer come back than those with lower numbers.

The researchers found that when immune cells were clustered together, the chance of recurrence within 10 years was 25 per cent higher than when immune cells were evenly dispersed. The chance of cancer returning within five years was 23 per cent higher in women with immune cell hotspots.

Prognostic tests already exist to predict the risk of recurrence for this group of patients, and the scientists found that combining the immune scores with the IHC4 test – which was developed by Breast Cancer Now scientists at the Institute of Cancer Research, London – could potentially out-perform the Oncotype DX test currently used in routine practice on the NHS.

“That this exciting immune tool could be added to existing prognostic tests to more accurately identify women at high risk of their breast cancer coming back is very promising. Automatically analysing the distribution of immune cells in a tumour is a big achievement, and if this approach is validated it could help doctors guide chemotherapy treatment.

“Many women live in fear of their breast cancer returning, and developing a way to precisely identify those at low risk could not only help alleviate this burden but allow many to be safely spared gruelling chemotherapy.

“Crucially, this study also highlights the importance of research into the role of the immune system in breast cancer returning. We now look forward to further studies to determine whether patients in the clinic could benefit from combining this new immune tool with existing predictive tests.”

The study, published in the Journal of the National Cancer Institute, was funded by the NIHR Biomedical Research Centre at The Royal Marsden NHS Foundation Trust and The Institute of Cancer Research (ICR), with support from Breast Cancer Now, Cancer Research UK, and Wellcome.